Thread-cutting mechanism for sewing machines



12, 1932. A, F F|F1ELD 1,841,102

T'HREAD CUTTING MECHANISM FOR SEWING MACHINES Filed March 15. 1930 :s sheet-sheet l Ja.- 12, 1932. A. F. FIFIELD 1,841,102

THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed March l5, 1930 3 Sheets-Sheet 2 Jan. l2, 1932 A. F. ,fFlFlELD v'111mm cuTTING` NEGNNNISN FOR SEWING MACHINES Filed March 15. 1950 3 Sheets-Sheet 5 Patented Jan. 12, 1932 UNITED STATES PATENT OFFICE ALBERT F. FIFIELD, yF NEWARK, NEW JERSEY, ASSIGNOR TO THE SINGER MANU- FACTURING COMPANY, OF 'ELIZABETH, NEW JERSEY, A 'CORPORATION 0F NEW JERSEY THREAD-CUTTING -MECHANISM FOR SEWING MACHINES Application filed March 15, 1930. Serial No. 435,996.

This invention relates to sewing machines and has for an object to provide an improved and simplified mechanism for nipping the beginning end of the needle-thread and for cutting the sewing thread or threads at the completion of a sewing operation.

Another object of the invention is to vprovide thread-nipping and -cutting mechanism which operates in such a manner as to insure uniformityin the finished product, i. e., uniformity in the lengths and disposition of the thread-ends.y

Vith the above and other objects in view,

as will hereinafter appear, the invention conl'sistis in the devices, combinations, andV arrangements of parts hereinafter described and claimed.

The several features of the invention and the advantages attained thereby will be readily understood by those skilled in the artffrom the following description of a .pre ferred embodiment thereof, taken in connection with the accompanying drawings, 1n which Fig. 1 is a side elevation of a Singer No. 114 Class button sewing machine embodying the invent-ion. Fig. 2 is a rear end elevation ofthe machine. Fig. 3 is a horizontal section on the line 3--3, Fig. 1, showing the usual vstop-motion overthrow mechani-smV of the machine in bottom plan. Fig. 4 is a section on the line 4 4, Fig. 1. Fig. 5 is a bottom plan view of the throat-plate of the machine and the thread-cutting and -nipping devices carried thereby.' Fig. 6 is a similar view with the device removed which cuts the finishing end `of the thread to better show the beginning threadend nipping and cutting devices; the nipping devicel being open. Fig. 7 is a similar view with both 4 0 thread-cutting devices removedand the nipping device in'closed, position, as in Fig. 5. Fig. Sis aperspective view of the mechanism under the throat-plate at the end of a sewing operation and before the threads are cut. Fig.f9 is a similar view at a slightly later` stage when the beginning thread-end is severed and before the last needle-thread loop on the looper is cut. Fig. 10 is a similar view at a still later stage when the worklimb of the last needlesthread loop is cut, and Fig. 11 is a perspective view of the nipper operating cam-mechanism.

The sewine' machine is constructed with a bed 1, standard 2, overhanging bracket arm 3 and head t carrying the reciprocating eyepointed needle 5 with which cooperates'thc rotary chain-stitch looper 6.' The needle 5 and looper 6 are connected as usual to be operated by the main-shaft 7, the period of operation of which is controlled by the usual stop-motion device including the tilting stop-motion lever 8 fulcrumed at 9 and carrying the belt-shipper 10 and upwardly spring-pressed stop-plunger 11.

Then the stop-motion lever 8 is shifted to running or dotted line position, Fig. 1, the stop-plunger 11 is carried inwardly from and out of engagement with the notched stopcam 12 on the main-shaft 7 and the drivingbelt (not shown) is shifted from the loose pulley 18 'to the tight pulley 14 to drive the machine. The lever 8 is held in running position by a latch 15 the tail of which is in position to be engaged by tripping points 16 on the usual feed-cam 17 to stop the sewing mechanism; the feedcam 17 being geared at 18 to the main-shaft 7 and making half a revolution for each sewing operation.

When the stop-motion lever 8 is released at the end of a sewing operation it springs to stopping or full line position Figs. 1, 2 and 3, and the plunger 11 is projected as usual into the notched stop-cam 12 to arrest the motion of the mainshaft 7. In this m0- tion of the lever 8,` its slotted lower end l8. Fig. 3, is moved inwardly along the pin 19 on the bell-crank lever 20 fulcrumed on the bed 1.

After the stop-motion plunger 11 drops into the notch of the stop-cam 12, the momentum of the main-shaft 7 imparts an overthrow or lateral motion to the plunger 11 and its carrier-lever 8, which carries the latter to dotted line position Fig. 2, thus swinging the bell-crank lever 20 to dotted line position, Fig. 3. This overthrow motion is largely absorbed by the usual buffer spring 21 which immediately restores the lever 8 to full line position, Fig. 2. At the end of a sewing operation therefore, the bell-cranklever 20 is `given .a momentary .impulse to dotted line position and return, Fig. 3, by the overthrow of the stop-motion device. The bellcrank lever 20 is forked to embrace a stud 22 on the thread-cutter-actuat'ing slide-bar 23 mounted in a groove 'in the side of the bed 1. This construction of stop-motion device having an overthrow motionV utilized to operate a thread-cutter is substantially that disclosed in the patent to Sullivan No. 777 ,564, of Dec. 13, 1904. n

The work-clamp is of the usual construction including the main lower bar 24 and worksupporting plate 25 and the upper buttongripping jaws 26 carried by the upper bar 27 fulcrumed at its rearward end in a block 28 carried by the main lower bar24. .logging movements are imparted to the work-clamp,

during the sewing operation by the usual connections with the feed-cam A17.

The thread-nipping and-cutting mechanism is as follows: y

Mounted ina slidewayin the under side of the throat-plate 29 is a slide-bar 30 carrying the hook-shaped thread-nipper spring 31 pressing upwardly against the under side of the throat-plate 2 9 adjacent the needle-` aperture 32. The slide-bar 30 is connected by the stud-pin 33 passing through a slot 34 in the throat-plate 29 to a link 35, Fig. 1, which is pivotally joined at 36 to the lower end of a lever 37 fixed to arock-shaft 38 journaled in the frame-bracket 39 screwed fast at 40 to the bracket-arm 3. The rock-shaft 38 also has iiXed to it the two-armed lever 41, 41 the free ends of the armsof which are positioned to be engaged by the respective cam-plates 42, 42 screwed to the peripheral edge face of the feed-wheel 17.,

rlhe arms 41, 41 are not disposed in the same vertical plane transverse to the axis of the cam-wheel 17 but are oifset from one another so that the lower arm 41 will Vtrack along the central zone of the edge of the caniwheel 17 where the short active iportions of the cams 42 are located', while the upper arm 41 tracks along the inner edge-zone of the cam-,wheel 17 where the cams 42 are ,located; i Y 1 vItfwill be noted that in the position of rest of the parts Figs. 1, and 11, one ofthe cams 42 is very close to the lower end of the leverarm 41. When ythe machine is started' and while the needleis on its first down-stroke but before its point reaches the work, the

cam 42 rocks the two-armed lever 41, 41 in a counter-clockwise direction, Fig. 1, to open the thread-end nipper 31 to the position shown in Fig. 6; the nosed upper end of the arm 41 being received in the gap 42X between the cams 42 in this movement. The needle continues its descent and rises to throw out a loop of thread which is seized by the looper 6 and drawn out as the needle continues its rise. n As soon as the needle point has risen clear of the path of the nipper 31, the twoarmed lever 41, 41 is given a reverse impulse to move theL nipper 31 from, the position shown inv F ig.v 6, to that shown in Fig. 7 during which movement the nipper-hook seizes the beginning end x of the needlethread pulled kdown by the looper and pinches it against the under-side of the throat-plate. The Athread-end nipper is thus moved from closed position to open position andback to closed positionv during the first` reciprocation of the .needle 5. 1t remains in closed position during therernainder of the sewing operation and occupies such'position when the machine is brought Vto rest by the stop-inotion device 8. y

Mounted on the under side of the throatplatev29, in underlapping relation with the nipper 31, is a ledger-blade 43 notched at 44 to provide a stationary vcutting-edge 45 for cooperation with the movable cutting edge 46 of a blade 47 screwed to the curved carrierarm 48 mounted on one arm 49 of a bell-crank lever fulcrurned at k50 on the throat-plate 29 and having fixed to its other arm 51 a studpin 52 embraced by the forked end of an arm 53 fixed to theslide-bar 23 which is given a Vto-and-fro impulse by the overthrow of the lstop-motion device, at the end cfa sewing operation, as previously described.

By the operation of the thread-end nipper 31 at the beginning of a sewing operation, the thread-end ai is carried into the'V notch 44 of the ledger-blade 43where it is in position to be trimmed by the action lof the shear-cutting edges 4'5, 46 at the end cfa sewing operation.

Pivoted at54 on the under side of the transverse ledgev forming a part of the bed 1 is a thread-cutting lever 56 having a knife-edge 57 and connected by a link 58 to the bar 53 which is rigid with the slide-bar 23. The knife and cutting-blade 47 arethus actuated simultaneously by the overthrow kmovement of the stop-motion device at the end of the sewing period; the knife 56 swinging about its pivot '54 so that its cutting-edge 57 engages andsevers thework-limbfg/ of the last needle-loop. When the work is removed, the thread-end'leading to the needle vis pulled outof'theworkY-and is long enough to start theV nekt'y sewing operation. 'l

By opening the -nipper before the needle completes its first descent andV .closing it as soonl as the looper has drawn-downl the beginning thread-end, there isavoided the neof uniformity in the sewing. This condition is aggravated by widening the nipper-hook or throat tol insure that it will catch the beginning thread-end.

By holding the beginning end of the thread throughout the sewing operation, there is avoided the danger of loosening the initial stitches from any cause during a sewing period as, for example, by friction of the needle or sewing thread against the beginning thread-end, which friction may draw the beginning thread-end to the upper side of the work at any timek during a sewing period f when a stitch is being made substantially coincident with one of the early formed stitches.

Also by providing an excess length of beginning thread-end and gripping and severing such thread-end, there is secured the advantages of surety in catching and holding the beginning thread-end and uniformity in the length of beginning thread-end in the nished roduct regardless of variations in P a e sewing conditions.

rihe invention is not to be understood as limited in its application to single-thread chain-stitch machines as it may to advantage' be employed in other types of sewing macliines, as will be obvious to those skilled in the art. y

Having thus set forth the nature of the invention, what I claim herein is:

l. In a sewing machine, the combination with stitch-forming mechanism, including a reciprocating needle, of a thread-end nipper, and means for opening said nipper prior to the initial penetration of the work by the needle and for closing said nipper to seize the beginning needle-thread end.

2. In a sewing machine, the combination with stitch-forming mechanism, including a reciprocating needle, of a thread-end nipper,

and means for opening said nipper in the initial descent of the needle and for closing said nipper to seize the beginning needlethread end.-

3. In a sewing machine, the combination with stitch-forming mechanism including a reciprocating needle, and a stop-motion dcvice, of a thread-end nipper, and means for opening said nipper prior to the initial penetration of the work by the needle and for closing said nipper to seize the beginning needlethread end, said nipper being held closed Vuntil the completion of the `final stitch of ay stitching-cycle.

4. Ina sewing machine, the combination with stitch-forming mechanism including a reciprocating needle, and a stop-motion device, of nipping means for holding the 'beginning end of the needle-thread substantially throughout the sewing cycle, and means for trimming the beginning end ofthe needlethread at the close of the sewing cycle while it is still held by said nipping means.

5. In a sewing machine, stitch-forming mechanism'including a reciprocating needle, a work-clamp, means including a feed-wheel for relatively moving the stitch-forming mechanism and work-clamp during the sewing, a stop-motion device for controlling the period of operation of the stitch-forming mechanism, means actuated by said feedwheel for nipping the beginning end of the needle-thread during the formation of the initial stitches of a sewing cycle, and means actuated by said stop-motion device for trimming the beginning end of the needle-thread at the close of a sewing cycle.

6. In a sewing machine, in combination, stitch-forming mechanism including a reciprocating needle, means (a) for trimming the beginning needle-thread end, means (b) for severing the last needle-thread loop, and common means for actuating said means (a) and (b) at the close of a sei 1ing operation.

7. In a sewing machine, stitch-forming mechanism including a. reciprocating needle, a throat-plate having a needle-aperture, a ledger-blade having a cutting-edge at one side of the needle-aperture, nipping means operating during the formation of the initial stitches to draw the beginning needle-thread end to one side of the needle-aperture and across said cutting-edge without trimming said thread-end, and a cutting-blade cooperating with said ledger-blade to trim said beginning thread-end at the close of a sewing operation.

8. In a sewing machine, a stitch-forming mechanism including a reciprocating needle, a stop-motion device, means for nipping the beginning end of the needle-thread, and means actuated by said stop-motion device for trimming said beginning end of needlethread while it is still held by said nipping means at the close of a sewing operation.

9. In a sewing machine, stitch-forming mechanism including a reciprocating needle, a stop-motion device having an overthrow movement, and a cutter for trimming the beginning end of the needle-thread connected to be operated by the overthrow movement of the stop-motion device.

10. In a sewing machine, stitch-forming mechanism including a. reciprocating needle, a stop-motion device having an overthrow movement, a cutter for trimming the beginning end of the needle-thread, a second cutter for severing the needle-thread of the final stitch of a sewing cycle, said cutters being reciprocating needle and a stopmoton de-.

vice, of e threed-endnpper, and npper operating means timed to open and Subsequently close seid npper during the rst complete reeprocaton of the needle to Seize the beginning needle-threedend and to hold the npper closed until the end of e. sewing period.

In testimony whereof, I have signed my nameto this specification. n ALBERT F. FIFIELD. 

